Plastic caps for plastic bottles are typically of the type disclosed in U.S. Pat. No. 3,338,446. The caps have a depending thin-walled skirt weakened approximately midway of its length with a circumferential score line so that the portion of the skirt below the score line may be torn off. The cap has two internal beads which extend circumferentially round the inside of the cap. These beads fit into grooves in the bottle neck and prevent the cap from being removed from the container. When both beads are in place the cap cannot be removed thereby preventing any tampering with the bottle contents. The lower bead is torn away when the lower skirt is removed. This then allows the cap to be easily pried over the upper bead to allow access to the contents. The upper bead remains with the cap thereby allowing the cap to be used repeatedly for reclosure until the contents of the bottle are exhausted.
There are several problems with the plastic caps of the prior art. A major problem is the splitting of the lower portion of the cap when it is forced onto the bottle neck. The score line for the tear-away lower section extends diagonally through the lower portion of the cap skirt and terminates at its rim. This score line weakens the cap rim and when pressure is exerted in an attempt to push the cap onto the bottle, the cap rim often tears along this score line. Bottles with torn rims must be removed from the packaging line, the cap manually removed and the bottle and contents recycled. This tearing problem, referred to as cap splitting, is a substantial burden and significantly increases operating expenses.
Another problem with the prior art caps is the difficulty by the consumer in tearing the lower skirt from the cap. The problem in caused, in part, by the manufacturer when it strengthens the score line for the purpose of reducing cap splitting as discussed supra. By strengthening the score line, the amount of force or difficulty required to tear the lower skirt from the cap is proportionately increased.
In addition, the score line as it extends diagonally through the lower skirt of the cap, must penetrate the lower bead which extends circumferentially around the inside of the skirt. Because the bead increases the thickness of the skirt at this point, the score line does not cut into the skirt as deeply thereby increasing the difficulty in tearing the lower skirt from the cap.
Another problem existant with the prior art caps is the loose fit of the cap onto the bottle neck. A tight fit between the cap and the bottle is essential for a good seal. Although the prior art caps could be made to fit more tightly onto the bottle, such an improvement would result in a greater number of cap splitting. Thus an improvement in fit or seal is off-set by an increase in split caps and operating costs.
Recently an improved tamper-proof cap was disclosed in U.S. Pat. No. 3,927,784 to the inventor herein which eliminated the cap splitting problems. In this cap a thin walled outer skirt was weakened along two circumferential score lines which formed a cylindrical band around the skirt below the first bead. When the band is removed, by way of a convenient tab, the lower skirt containing the lower bead is left on the container neck completely severed from the main cap portion. The upper or cap portion could then be conveniently used again and again as a cover until the container contents are consumed.
This cap while representing a significant improvement over the prior art, created other problems in certain applications. For example if a cap is defectively manufactured and is inadvertantly inserted onto a full container, the cap must be removed and the container recaped. The problem with the improved cap is that the lower portion of the skirt is difficult to remove from the container neck to accomodate recycling the container.
In addition, the improved cap cannot be used satisfactorily on returnable containers since the lower portion of the skirt is difficult to remove from the neck of the container.
A need thus exists for a tamper-proof cap which can be used repeatedly for reclosure, which can be inserted onto the bottles without cap splitting, which can be completely removed from the bottle without great difficulty, which has a tight fit or good seal and which is relatively easy to produce and inexpensive to manufacture.
It is therefore an object of this invention to provide an improved plastic cap.
It is an additional object of this invention to provide an improved plastic cap which does not split when inserted onto a container.
It is a further object of this invention to provide an improved plastic cap which may be completely removed from the container without difficulty.
Another object of this invention is to provide an improved plastic cap which fits tightly on the container neck and provides improved sealing of the container contents.
It is a further and additional object of this invention to provide a container and improved cap combination.
Other related and additional objects of this invention will be apparent from the drawing, the following description of the invention and appended claims.